The LATTE study will pick up where ATAC left off to follow a number of post-menopausal women with breast cancer who were randomised to receive either anastrozole or tamoxifen in the ATAC Trial and not known to have died or withdrawn consent before April 1st 2009. Since ATAC was a nationwide study, the women of LATTE will also reside and receive their follow-up care in various areas of the country. There will not be any vulnerable groups participating in this study.